Developer composition for a light



United States Patent 3,091,533 DEVELOPER COMPOSITION FOR A LIGHT SENSITIVE LITHOGRAPHIC PLATE George R. Hodgins, Scaford, N.Y., assignor to Litho Chemical and Supply Co. Inc., Lynhrook, Long Island,

N.Y., a corporation of New York No Drawing. Filed May 22, 1958, Ser. No. 736,966

' 2 Claims. (CI. 96-49) The present invention relates to a novel lithographic plate and its preparation and more particularly to a lithographic plate comprising an aluminum sheet provided with a certain combination of coatings which produces important new advantages and results.

Coated aluminum planographic printing plates are known wherein a silicated aluminum sheet is coated with a light-sensitive diazo resin which, when exposed to ultraviolet light through a stencil or negative, reacts in the exposed portions, expelling nitrogen from the molecule and forming a water-insoluble hydrophobic and organophilic material tightly bonded to silicate film of the aluminum sheet, the resins being thereafter washed away from the unexposed areas to leave the silicate film bare in such areas. In other plates which have had limited commercial use, a stretchable backing material such as paper or plastic has been used and coated with a colloidal material, but such are only satisfactory when used promptly, since they cannot be stored without undergoing distortion or deterioration. The aluminum coated sheets have represented an improvement over the use of stretchable backing material, but have fallen short of a completely successful solution of the problems involved due, at least, in material part to procedural and compositional shortcomings.

An important disadvantage of prior plates and their production resides in the fact that changes had to be made and adapted for aluminum plates with different grain depths so that a single silicating solution could not be used and the method of application required adjustment for each different grain depth.

Another disadvantage is that standard diazo resin solutions do not provide the desired characteristics of good photographic speed and high resistance to abrasion and chemical attack and do not ensure accuracy and long duration of operation as they deteriorate rather rapidly, require relatively long exposure times and produce images deficient in hardness.

Further disadvantages result from the nature of the lacquer and developer formulations used in the production of such plates so that the length of n is less than is desired and reproduction of fine detail is not obtained.

Objects and advantages of the present invention are to overcome the foregoing and other recognized disadvantages of prior practices and to produce lithographic plates having advantages unique to themselves and especially to provide accurate and stable lithographic plates having excellent physical, chemical, photographic and reproduction characteristics such as have not been heretofore attained. Still other objects and advantages will be appreciated from the following description or will be understood by those skilled in this art.

A lithographic plate according to the invention comprises an aluminum sheet or plate at least one surface of which is provided with a silicate film formed in situ thereon by the reaction of the aluminum sheet or plate with an aqueous alkali silicate solution and then washed free of residual alkali. The aqueous alkali silicate solution is a suspension of powdered sodium silicate having a ratio of SiO :Na O of 1:328 in a 42 Baum sodium silicate solution having a ratio of SIOgZNagO of 1:3.25. On the thus silicated aluminum surface there is applied a light-sensitive coating, adherent to the silicate film,

lCC

formed from a hydro-alcoholic solution of the watersoluble condensation product of p-diazo diphenylamine and formaldehyde, superpolyamide nylon resin (which is a copolymer of Nylon 6, Nylon 6/6 and Nylon 6/10 as defined in my Patent No. 2,826,501 and hereinafter) and a non-ionic surface active agent having the following preferred composition, by weight:

0.11% of the water-soluble condensation product of pdiazo diphenylamine and formaldehyde,

0.94% of soluble superpolyamide nylon resin,

0.01% of polyethylene glycol tertiary-dodecylthioether,

17.15% of water,

76.35% of denatured ethyl alcohol, and

5.44% of furfuryl alcohol,

the light-sensitive coating having been exposed in preselected areas to a source of ultra-violet light. A lacquer is applied to said coating, the lacquer comprising a pigmented organic solvent containing a furfuryl alcohol condensate or resin (as hereinafter defined) and an epoxy resin which is a condensation polymer of epichlorhydrin and bis-phenol and having the following preferred weight/volume composition:

Epoxy resin g r ams 71 CH COOCH,CH OC H 1TllIIlllIe1'S... 2000 Xylene ..do 2000 Furfuryl alcohol condensate grams.... 83 The calcium salt( of formula below) do following which the plate is developed wia; hydroalcoholic solution of gum arabic, phosphoric acid, a substituted phenol and a wetting agent having the following preferred composition, by volume:

Water 17 gallons, 86 ounces. 14 Baum gum arabic solution 3 gallons, 15 ounces. Sodium lauryl sulfate (10%) 4 gallons, 20 ounces. Phosphoric acid 315 milliliters. n-Octyl alcohol 15.9 ounces. p-Chlorophenol 16.6 ounces.

to remove unexposed areas of the light-sensitive coating.

The furfuryl alcohol condensate or resin (Durez Resin #14383) is a furfuryl alcohol polymer having a viscosity at 25 C. in the range of 10,000 to 16,000 cps. and a specific gravity of 1.162 to 1.182. lts actual molecular weight has not been determined but is estimated to be about 500-700.

The complete procedure for preparing the lithographi plate is illustrated by the following example:

Example Aluminum foil or sheet having a thickness of from 0.005 to 0.025 inch is cleaned and degreased with trichlorocthylene or similar solvent such as chloroethane." The degreased aluminum foil or sheet is then brush grained or ball grained to produce a matte surface, cleaned in an inhibited alkaline cleaning solution, such as a mixture of trisodium phosphate, detergent and sodium metasilicate, rinsed thoroughly and then treated on one or both surfaces with a silicate solution that reacts with the aluminum to provide thereon a film of silicate. The silicating of the metal is carried out by running the sheet or foil of aluminum through the solution from a roll, by dipping or immersing the individual sheets in the solution or by passing the sheets through a roller coater.

While various silicate solutions can be used successfully, such as Ludox" and others mentioned in the literature, the best and preferred silicate solution is a mixture of a suspension of powdered sodium silicate (374 grams) having the following analysis:

of which Philadelphia Quartz SS-65 Powder is an exempla'y material, in 42 Baum sodium silicate solution (2 gallons) having the following analysis, exclusive of water:

Sim-27.89% sio, Na,O8.58% N310 the powdered sodium silicate remaining suspended in the 42 Baum sodium silicate solution. The above mixture is diluted with water to any desired concentration depending on the type of grain on the aluminum surface. It has been found that for fine or brush grain plates, the above mixture should be diluted with water to a total volume of 28 gallons, the plates being immersed at a temperature of 82" C. for a period of 1 to 2 minutes. For ball grained plates, a dilution to 4 gallons is suitable since a heavier silicate film is desired. The solution is applied at room temperature by means of a roller and then sealed by heating to a temperature in the range of 110 to 150 C. The plate is then rinsed with hot water at 60 C. after the heat sealing. The thus silicated metal is rinsed thoroughly with water at 60 C. to remove residual alkali which might cause decomposition of the subsequently applied diazo resin coating.

The silicated metal is next coated with a light-sensitive diazo-nylon resin solution formulated according to Patent No. 2,826,501 the contents of which are hereby made a part hereof. The solution is applied just before the plate is processed or the metal may be pre-coated with the solution and then stored in the dark until required. The solution contains the following constituents in substantially the following proportions, by weight:

0.11% of the water-soluble condensation product of p-diazo diphenylamine and formaldehyde,

0.94% of soluble superpolyamide nylon resin,

0.01% of a non-ionic surface active agent (100%),

17.15% of water,

76.35% of denatured ethyl alcohol, and

5.44% of furfuryl alcohol.

The non-ionic surface active agent is polyethylene glycol tertiary-dodecylthioether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan mono-palmitate, or an alkyl aryl polycther alcohol. The diazo condensation product is, for example, Diazo Resin #4 or Diazo Lith #1 and is water-soluble, of low degree of polymerization and of narrow range molecular weight. It may be made according to Patent No. 2,063,631. The nylon resin (Zytcl #61) is a co-polymer of poly caprolactam (Nylon 6), hcxamethylene-diamine-adipic acid (Nylon 6/6) and hexamethylenc-diamine-sebacic acid (Nylon 6/10). The water in the solution may range from 17% to 20% and the furfuryl alcohol may range from 1% to 8%.

The diazo-nylon resin coated aluminum, after drying, is exposed through a negative to a source of ultra-violet light such as a carbon arc lamp such as a 35ampere carbon are for two minutes at a distance of 36 inches.

After exposure, a lacquer is applied to the plate as described in copending application Serial No. 714,508, filed February 11, 1958, in the names of Hodgins and Timmerman. This lacquer is a combination of an epoxy resin and a furl'uryl alcohol resin. The epoxy-furfuryl alcohol resin lacquer has the following formulation:

Epon 1001 Resin grams 71 Cellosolve acetate milliliters 2000 Xylene ..do- 2000 Durez Resin #14383 grams Uncas Maroon do The formulation given above produces an optimum film thickness of lacquer, but variations of by weight of either resin have been successfully used without adversely affecting the image and such variations are within the scope of the invention.

It has further been found that toluene or benzene can be substituted by xylene and that Cellosolve or Methyl Cellosolve can be substituted for Cellosolve Acetate. The Uncas Maroon pigment can be replaced by other pigments, particularly by Toluidine Toner #29, Pigment Scarlet #ZSAD, or Pigment Scarlet #829.

Toluidine Toner #29 is a red pigment prepared by diazotizing m-nitro-p-toluidine and coupling it to an alkaline solution of p-naphthol.

Pigment Scarlet #25AD and #829 are precipitations of the well known azo dyestuff Pigment Scarlet (Color lndex No. 216) with metallic mordants. In the case of #ZSAD, the metals are zinc, barium and aluminum and in the case of #829 the metals are lead, barium and aluminum. The exact structural formulas are not known.

The Epon 1001 Resin may be replaced by other epoxy resins such as Bakelite EKR 2002 resin, each of which has an epoxide equivalent of 450-525 (grams of resin containing one gram-equivalent of epoxide).

Any suitable epoxy resin may be used. Epon 1001 Resin has been found to be best but this may be replaced by Bakelite EKR 2002 resin or other epoxy resin. The Cellosolve constituent may be Cellosolve itself, Methyl Cellosolve or Cellosolve Acetate. Any one of the organic solvents xylene, toluene or benzene may be satisfactorily used, xylene being preferred. The pigment is preferably Uncas Maroon which may, however, be replaced by other pigments such as Toluidine Toner #29 or Pigment Scarlet #ZSAD or #829.

An epoxy resin having an epoxide equivalent of 450- 525 has been found to be optimum and thus is preferred, but other epoxy resins have been used satisfactorily having epoxide equivalents (grams of resin per gram mole of epoxide) in the range of to 4000, viz.:

Epoxide Name: Equivalent Epon 828 175-210 Epon 1001 450-525 Epon 1004 870-1025 Epon 1009 2400-4000 Araldite 502 263 Araldite 6005 192 Araldite 6030 227 Araldite 6040 270 Araldite 6060 417 Araldite 6071 485 Araldite 6075 715 EKR 2002 450-525 The furfuryl alcohol resins are made as described in The Furans," A.C.S. Monograph #119, pages 783-790. The plate is then developed with a developer solution of gum arabic and phosphoric acid to remove the unexposed areas of the diazo-nylon coating, the developer having the following composition:

Water 17 gallons, 86 ounces. 14 Baum gum arabic sol-ution 3 gallons, 15 ounces. Duponol solution 4 gallons, 20 ounces. Phosphoric acid (85%) 315 milliliters. n-Octyl alcohol 15.9 ounces. p-Chlorophenol 16.6 ounces.

Duponol is sodium lauryl sulfate, technical grade. Other anionic and non-ionic wetting agents work satisfactorily but sodium lauryl sulfate is preferred due to its low cost and effectiveness. The n-octyl alcohol may be replaced by n-hexyl alcohol, n-heptyl alcohol, 2-octanol or decanol, viz. a 6 to 10 carbon atom alcohol. Aromatic constituents such as geraniol, cedrol and iso-bornyl acetate may be used to mask the odor of the p-chlorophenol which substituted phenol may, if desired, be replaced by pentachlorophenol, 2,3,4,6-tetrachlorophenol, 2-chloro-4-phenyl phenol, 2,4,6-trichlorophenol, 2,4,5-trichlorophenol or o-phenyl phenol, although p-chlorophenol is most effective.

The above developer has been found to be an important improvement over the prior use of gum arabicphosphoric acid solutions since the wetting agent (Duponol) aids in the suspension of the developed material as well as speeding developing action. The phioro phenol produces complete removal of the film from the unexposed areas.

It will be appreciated from the foregoing that a lithographic plate according to the present invention and prepared by the above-described process represents a new and unique entity having properties and characteristics not heretofore obtained and presenting manifold advantages due to the coaction and interaction of the various components going into its make-up. The invention has the particular advantage that a single silicate solution can be used on aluminum plates having different grain depths and types by varying the dilution of the silicate solution and selecting its mode of application.

Another advantage is that, after silicating, the plates can be roller coated with the scnsitizer or can be coated with the diazo-nylon solution at the customer's premises and by following the latter, larger stocks of aluminum can be kept on hand than if pro-coated plates are stocked since coated plates become gradually deteriorated by heat. In this connection, the diazo-nylon solution occupies less volume than the aluminum plates and is easier to cool. A further advantage is that the special Eponfurfuryl alcohol lacquer increases the length of run of the diazo-nylon coating which, itself, requires less exposure, is more stable in solution and yields harder images than conventional diazo resin alone.

The invention is defined by the appended claims.

What is claimed is:

1. A developer for a light-sensitized lithographic plate comprising the following constituents in substantially the following proportions:

Water L.. 17 gallons, 86 ounces. 14 Baume gum arabic solution 3 gallons, 15 ounces. Sodium lauryl sulfate 10% aqueous solution, by weight 4 gallons, 20 ounces. Phosphoric acid aqueous solution, by weight 315 milliliters. n-Octyl alcohol 15.9 ounces. p-Chlorophenol 16.6 ounces.

2. A developer for a light-sensitized lithographic plate comprising the following constituents in substantially the following proportions:

Water 17 gallons, 86 ounces. Gum arabic solution 14 Baum 3 gallons, 15 ounces. Wetting agent 10% aqueous solution by weight 4 gallons, 20 ounces. Phosphoric acid 85% aqueous solution, by weight 315 milliliters.

15.9 ounces.

References Cited in the file of this patent UNITED STATES PATENTS 2,714,066 Jewett et a1. July 26, 1955 2,754,219 Hall July 10, 1956 2,826,501 Hodgins Mar. 11, 1958 2,865,873 Hodgins Dec. 23, 1958 FOREIGN PATENTS 761,493 Great Britain Nov. 14, 1956 

2. A DEVELOPER FOR A LIGHT-SENSITIZED LIGHOGRAHIC PLATE COMPRISING THE FOLLOWNG CONSTITUENTS IN SUBSTANTIALLY THE FOLLOWING PROPORTIONS: WATER 17 GALLONS, 86 OUNCES. GUM ARABIC SOLUTION 14* BAUME - 3 GALLONS, 15 OUNCES. WETTING AGENT 10%% AQUEOUS SOLUTION BY WEIGHT 4 GALLONS, 20 OUNCES. PHOSPHORIC ACID 85%% AQUEOUS SOLUTION, BY WEIGHT 315 MILLITERS. AN ALCOHOL SELECTED FROM THE GROUP CONSISTING OF N-HEXYL ALCOHOL, N-HEPTYL ALCOHOL, N-OCTYL ALCOHOL, 2-OCTANOL AND DECANOL 15.9 OUNCES. A DEVELOPER-PROMOTING SUBSTITUTED PHENOL SELECTED FROM THE GROUP CONSISTING OF P-CHLOROPHENOL, PENTACHLOROPHENOL, 2,3,4,6-TETRACHLOROPHENOL, 2CHLORO-4-PHENYL PHENOL, 2,4,6TRICHLOROPHENOL, 2,4,5-TRICHLOROPHENOL AND O-PHENYL PHENOL 16.6 OUNCES. 